Effect Measure

Helen Branswell has a story about a battle being waged among virologists and occupational health specialists regarding how influenza is spread from person to person:

Later this week virologists, infection control specialists and occupational health experts from Canada, the U.S. and Britain will gather in Toronto to start trying to answer a question that is the source of a polarized debate among them.

How does influenza spread from one person to the next in hospitals? Is it mainly transmitted by hand-to-hand contact and virus-laced droplets sneezed or coughed from the respiratory tracts of the infected? Or do those expelled viruses hover in the air for longer periods and over greater distances than heavy droplets, making airborne transmission a factor in flu’s spread?

It may sound like a debate over how many viruses can dance on the head of a pin. But this is no esoteric exercise. The outcome could determine how many health-care workers will be well enough – or willing – to look after the rest of us when the next flu pandemic strikes. (Helen Branswell, Canadian Press)

The practical issue is being framed this way. If flu is “airborne” (meaning that the virus is in very tiny aerosol droplets and remains suspended in the air for extended periods), then health care workers should use so-called N95 respirators. If not, then surgical masks are adequate.

We think this is bad framing. N95 respirators need to be fitted properly if they are to protect health care workers. Anyone working in close quarters with influenza patients, for example, intubating them or sunctioning them or doing respiratory hygiene on them, should be wearing a properly fitted N95 respirator, whatever the predominant droplet size. A surgical mask won’t protect them. On the other hand, if the virus remains suspended and viable for long periods in the air, then an N95 mask would have to be worn nearly constantly and not just in the hospital. Even then it might not protect sufficiently, depending upon particle size and infectivity of the virus. Small particles have high surface area to volume ratios and dry out very rapidly, becoming even smaller. It is not inconceivable they could be predominantly submicron size. The best protection in those circumstances might be ultra violet light germicidal irradiation (UVGI).

In our view this is a more fruitful direction than arguing whether N95 masks should be worn by health care workers. N95s should be used by all health care workers performing procedures on influenza patients. It is an open question whether they should be used on open wards, hospital rooms or clinics where patients are being cared for. The masks are not meant to be reused, need to be properly fitted and are uncomfortable for many people. Their efficacy in the more general health care settings is unknown. However if providing these masks makes it more likely health care workers will show up for work, then efforts should be made to do so, but that is a different question. It is our opinion they are not useful for the general environment, although we cannot prove this one way or another.

UVGI should be investigated for area disinfection of health care facilities and possibly other public venues if very small particle aerosols are thought to be a significant mode of spread. UVGI requires further study, which we suggest be undertaken with some urgency. Meanwhile, the mask arguments seem more like rearranging the deck chairs on the Titanic.

Comments

#1 M. Randolph Kruger
October 23, 2006

I guess the dilemma we face is that there is a full on debate as to what to do about this stuff. WHO has a whole several pages on how to use PPE and where to use it. They recommend M95′s and face shields. On the other hand I have a friend who is the director of DHS and they went to a gig in Mississippi last month where some bozo told them that a contaminated mask could be reused if you put it into a bag and sealed it for three days…Huh?

The straight skinny is what the people need to hear and see right now. I keep looking at the graphics that the WHO Pac Region is posting and that graph is continuing to climb, the color codes for every country are adding up to wider and higher each month. To boot its winter setting in.

Time for the BS to end. If they need full face plate masks with NBC filters like I have then they need to say it. Its uncomfortable as hell but its overkill. Underkill will get you killed or terribly sick in a pandemic which is the same as a death sentence.
#2 epifreek
October 24, 2006

I agree that UVGI should be looked at, but there seems to be remarkably little interest in this technology so far.

N95 respirators can be reused and are reused (by the same healthcare worker) in the care of TB patients. The difference between TB and influenza is that TB bacteria only cause disease when they are inhaled and surface contamination of the respirator is not an issue during the care of TB patients.

However, influenza virus can cause disease when it is inhaled and also when the virus is inoculated into the mucous membranes of the eyes, nose, or mouth (either by being deposited there from a cough or sneeze or by contaminated hands).

During the care of infectious influenza patients, the surface of the respirator could become contaminated with virus. Handling a contaminated respirator could then contaminate the hands, which could then inoculate a mucous membrane. It is possible that this is how some healthcare workers became infected during the SARS outbreak.

If/when there is a shortage of N95 respirators during a pandemic and no other method has been devised to decontaminate them, letting them sit for 2-3 days before they are reused should allow any virus on the surface to die so that healthcare workers don’t contaminate themselves when handling used respirators.
#3 limestone
October 24, 2006

Could you speak to where UVGI is being used effectively at the present? Is it used in operating rooms between surgeries? I seem to remember Andromeda Strain-like decontamination procedures make use of UVGI in high-risk lab sites. Surely it doesn’t have to be an expensive proposition to provide light at the proper wavelength at the adequate doses. I suppose someone has to figure out the adequate doses to zap the viruses… (Everybody, cover your eyes when the klaxon sounds…..)
#4 AF
October 24, 2006

Somewhat related to the topic at hand, but what type of masks should civilians/citizens use for preventive measures in the case of a widespread flu pandemic? N95? N100?
#5 Tom DVM
October 24, 2006

Answer: All of the above.

It is not for Governments and Hospital Managers to talk amongst themselves and then impose their decision on healthcare workers…at least in Canada, that option ended with SARS.

It is time for Governments and Hospital Managers to directly engage their cherished employees, sector by sector, hospital by hospital, community by community…what will be required by them to feel protected enough to provide a public service is difficult circumstances.

N95 masks don’t have a best before date…
#6 JAD
October 24, 2006

Revere,
As a researcher for an engineering firm that designs UVGI systems for hospitals, I find that some infection control practitioners (ICPs) are skeptical that influenza is spread via the airborne route. They seem to be stuck on the idea that all infection is contact or droplet, period! They have neither the time, resources nor inclination to examine new information on the topic.
An excellent (and succinct) review of arguments for airborne transmission is found in the November 2006 issue of the CDC’s Emerging Infectious Diseases journal. The study’s (http://www.cdc.gov/ncidod/EID/vol12no11/06-0426.htm) author is a physician from the Hospital for Sick Children in Toronto. Perhaps the author’s experience with the SARS outbreak in Canada has influenced his perspective on airborne transmission.
The study notes that health officials in France and Australia already recommend N95 respirators for HCW dealing with an influenza outbreak.
In the case of a bird flu pandemic, consider a hospital’s ED waiting area. Typically, 80% of the air extracted from the waiting room is re-circulated within the hospital. Filtration for this air is designed to remove large contaminants (dust, hair, etc.) and cannot remove submicron pathogens. Filtration capable of arresting most airborne pathogens, such as HEPA, is too expensive to deploy throughout the hospital. The re-circulation of air causes pathogens to gather and grow on cooling coils and filters within the hospital’s ventilation system.
Our sampling/swabbing of hospital ventilation units routinely shows the presence of Pseudomonas, Serratia, Klebsiella, Stenotrophomonas, Acinetobacter, Staph Aureus and Streptococcus. When confronted with evidence that infection causing pathogens are residing and thriving inside air handling units that supply patient care areas, some ICPs still cannot see a link between this reservoir of pathogens and nosocomial infection within their facility.
While this is not a forum to trumpet UVGI, I would add that when configured properly, UVGI effectively disinfects this reservoir and significantly decreases the microbial load re-circulating within the hospital. It should always be used in conjunction with high efficiency filtration.
One positive side effect of H5N1 is that many in health care have re-examined their views on infection control and looked for innovative solutions. It is my belief that infection control is an environmental issue–that there is a chain of transmission. Aerosols are one link in that chain, a link whose importance is frequently under estimated..

Study cited: Tellier R. Review of aerosol transmission of influenza A virus. Emerg Infect Dis 2006 Nov. Available from http://www.cdc.gov/ncidod/EID/vol12no11/06-0426.htm
#7 sharpstick
October 24, 2006

I’ve seen UVGI installations in components of building HVAC systems but have questions about their efficiency. The systems are advertised as a preventive measure against microbial growth on surfaces inside of air handlers. Some even seem to claim that the systems are effective against potential bioterrorism agents like anthrax and smallpox. I understand the theory and mechanics of the systems but have serious doubts about their ability to effectively render harmless the large volumes of air passing through them.
#8 crfullmoon
October 24, 2006

Politicians and Hospital Administrators, bureaucrat by bureaucrat, should be on site, in their surgical masks, and provide care themselves, in the panflu units. (And transport bodies for burial.)

Politicians and Pandemic “Planners” should ‘fess up now to the public that the steps taken now at home may be the only ones the public can count on for the next few years.

A preparing public would pose fewer problems; get them involved in their communities’ coping solutions.
#9 slovenia
October 24, 2006

AF–I bought 50 N98 respirators with eye guards because my wife, who is a pediatrician, will be on the front line in a pandemic and the possibility of a mask shortage is real. The last time I visited the fluwiki there was lots of discussion about which masks were best. Go there for more information. You will also find discussion regarding the sterilization of used masks.
As evidenced by the Branswell article and several of Revere’s prior postings, there is controversary over whether masks will help at all. But the investemnt is small and, if they do help, I’ll be glad I bought them.
#10 Lenn
October 24, 2006

The CDC’s journal Emerging Infectious Diseases has an article that reviews research into transmission of influenza. the URL for it is here: http://www.cdc.gov/ncidod/EID/vol12no11/06-0426.htm.
#11 Charles Roten
October 24, 2006

Sorry, Lenn.

But that URL you just posted handed me a HTML 404 error (“page not found”) when I tried to use it.
#12 Lenn
October 24, 2006

My bad. I forgot that I should not put a period after the URL. The system added it to the link. Try the following:

http://www.cdc.gov/ncidod/EID/vol12no11/06-0426.htm
#13 Ann
October 24, 2006

I would not approve of letting the N95 masks sit for two or three days and then reusing them. There are a too many unknowns to take risks like that.
#14 M. Randolph Kruger
October 24, 2006

Slov old son. My suggestion is that your very gutsy wife who will work during this when it comes get a full face place with a full NBC ensemble. She needs to treat it as a biowarfare incident gone seriously wrong. Pain in the ass to wear for even 4 hours a day and its not 100% insurance but damned close. The suits are repairable even if torn, the masks are compatible with the military filters. She could go for weeks at a time, doff and don’ing the ensemble, decontaminating, and using the same stuff over and over. She would also “know” it was as clean as possible. It would also give her the ability to move about in what essentially would be a fully biohazardous environment. She leaves the disease at the office or in a bin outside. A washed down suit thats left in a garbage can overnight with a cup of bleach open in it kills everything by gas.

The equipment is out there for fairly cheap. If you need some more help on this then hit me at:

memphisservices@bellsouth.net

Tell her that I said she has it to go in my book.
#15 MoM
October 25, 2006

Randy. Just a suggestion, but the spambots mine blogs for e-mail addys which they then sell to the spammers. Better to post yours as memphisservices (at) bellsouth (dot) net. There are places on the web that will turn it into HTML characters that work also. using & # 0 6 4 ; without the spaces for the @ and & # 0 4 6; for the dot can work as well.
Better yet to get a “freebie (hotmail, Yahoo or gmail) address to use for just such occasions, and keep your ISP addy for friends only.
#16 Lenn
October 25, 2006

Slov,

I’m whole-heartedly with Randy on this one. His advice is very good. If you treat this disease as a worse case situation and protect accordingly, then you will defend against lesser threats. On the other hand (and rather obviously), doing the opposite will not protect against greater threats.
#17 Nurse
October 25, 2006

Heres the bottom line, no N95 masks = very few HCWs period end of story. They can argue discuss test or whatever NO HCW is stupid enough to work with H5N1 without NEW fitted N95 masks. We are not about to believe any test study or whatever that is trotted out that says we need anything less, it just isnt going to fly.

BTW my employer has exactly zero N95 masks. The life of the HCW is deemed not worth the $1.50 or so per mask. Think the staff is going to show up in any significant numbers? Just hope nobody you care about is a patient of this company, or many like it.
#18 Lenn
October 26, 2006

I don’t blame you one bit, Nurse. If it were me, I’d insist on N95s or higher and I’d stand my ground on it.

If they don’t spring for those, then there will be a lot more dead people… dead doctors… dead nurses… and dead patients who don’t have doctors or nurses to take care of them because those doctors and nurses are too busy being dead.
#19 tan06
October 26, 2006

In my experience the N95 masks have to be taped along the outside lines because they most of the time don’t fit very well.

I remember (closing Schools) the question about UV C light. Is it the same as the above mentioned UV GI light?

And my second question about the UV light as a proposed means to be added to masks is about the effects on the skin. Is it safe, or should it be used for other surfaces only? Because some kinds of UV light can give blisters and sunburn in just less than one hour.

Finally, when we are talking about ventilators, nurses and doctors doing their jobs (or not being able to do so) is there some kind of energy source to get these ventilators and UV lamps working at all when electricity falls out?
This is only relevant when a pandemic is there, of course.